_Of_ LEAD.
Next to Gold and Mercury Lead is the heaviest of all metalline
substances, but in hardness is exceeded by every one of them. Of all
metals also it melts the easiest except Tin. While it is in fusion
there gathers incessantly on its surface, as on that of Tin, a blackish
dusty pellicle, which is nothing but a calx of Lead.
This calx further calcined by a moderate fire, the flame being
reverberated on it, soon grows white. If the calcination be continued
it becomes yellow, and at last of a beautiful red. In this state it
is called _Minium_, and is used as a pigment. _Minium_ is not easily
made, and the operation succeeds well in large manufactures only.
To convert Lead into _Litharge_, which is the metal in a manner half
vitrified, you need only keep it melted by a pretty strong fire; for
then as its surface gradually calcines, it tends more and more to
fusion and vitrification.
All these preparations of Lead are greatly disposed to perfect fusion
and vitrification, and for that purpose require but a moderate degree
of fire; the calx or earth of Lead being of all metalline earths that
which vitrifies the most easily.
Lead hath not only the property of turning into glass with the greatest
facility, but it hath also that of promoting greatly the vitrification
of all the other imperfect metals; and, when it is actually vitrified,
procures the ready fusion of all earths and stones in general, even
those which are refractory, that is, which could not be fused without
its help.
Glass of Lead, besides its great fusibility, hath also the singular
property of being so subtile and active as to corrode and penetrate the
crucibles in which it is melted, unless they be of an earth that is
exceeding hard, compact, and withal very refractory: for Glass of Lead
being one of the most powerful fluxes that we know, if the earth of
the crucible in which it is melted be in the smallest degree fusible,
it will be immediately vitrified; especially if there be any metallic
matter in its composition.
The great activity of Glass of Lead may be weakened by joining it with
other vitrifiable matters: but unless these be added in a very great
proportion, it will still remain powerful enough to penetrate common
earths, and carry off the matters combined with it.
On these properties of Lead, and of the Glass of Lead, depends the
whole business of refining Gold and Silver. It hath been shewn, that as
these two metals are indestructible by fire, and the only ones which
have that advantage, they may be separated from the imperfect metals,
when mixed therewith, by exposing the compound to a degree of fire
sufficiently strong to vitrify the latter; which, when once converted
into glass, can no longer remain united with any metal that has its
metalline form. But it is very difficult to procure this vitrification
of the imperfect metals, when united with Gold and Silver; nay, it
is in a manner impossible to vitrify them entirely, for two reasons:
first, because most of them are naturally very difficult to vitrify;
secondly, because the union they have contracted with the perfect
metals defends them, in a manner, from the action of the fire, and that
so much the more effectually as the proportion of the perfect metals
is greater; which being indestructible, and in some sort coating over
those with which they are alloyed, serve them as a preservative and
impenetrable shield against the utmost violence of fire.
It is therefore clear, that a great deal of labour may be saved, and
that Gold and Silver may be refined to a much greater degree of purity
than can otherwise be obtained, if to a mixture of these metals with
Copper, for instance, or any other imperfect metal be added a certain
quantity of Lead. For the Lead, by its known property, will infallibly
produce the desired vitrification; and as it likewise increases
the proportion of the imperfect metals, and so lessens that of the
perfect metals, in the mass, it evidently deprives the former of a
part of their guard, and so effects a more complete vitrification. In
conclusion, as the Glass of Lead hath the property of running through
the crucible, and carrying with it the matters which it has vitrified,
it follows, that, when the vitrification of the imperfect metals is
effected by its means, all those vitrified matters together penetrate
the vessel containing the fused metalline mass, disappear, and leave
only the Gold and Silver perfectly pure, and freed, as far as is
possible, from all admixture of heterogeneous parts.
The better to promote the separation of such parts it is usual to
employ, in this process, a particular sort of small crucibles, made of
the ashes of calcined bones, which are exceedingly porous and easily
pervaded. They are called _cupels_, on account of their figure, which
is that of a wide-mouthed cup: and from hence the operation takes its
name; for when we refine Gold and Silver in this manner we are said
to _cupel_ those metals. It is easy to perceive that the more Lead is
added the more accurately will the Gold and Silver be refined; and
that so much the more Lead ought to be added as the perfect metals are
alloyed with a greater proportion of the imperfect. This is the most
severe trial to which a perfect metal can be put; and consequently any
metal that stands it may be fairly considered as such.
In order to denote the fineness of Gold, it is supposed to be divided
into twenty-four parts called _carats_; and Gold which is quite pure
and free from all alloy is said to be twenty-four _carats fine_; that
which contains 1/24 part of alloy is called Gold of twenty-three
carats; that which contains 2/24 of alloy is but twenty-two carats; and
so on. Silver again is supposed to be divided into twelve parts only,
which are called _penny-weights_: so that when absolutely pure it is
said to be twelve _penny-weights fine_; when it contains 1/12 of alloy,
it is then called eleven penny-weights fine; when it contains 2/12 of
alloy, it is called ten penny-weights fine, and so on.
In treating of Copper we promised to shew, under the article of Lead,
how to separate it from Iron. The process is founded on that property
of Lead which renders it incapable of mixing and uniting with Iron,
though it readily dissolves all other metalline substances. Therefore,
if you have a mass compounded of Copper and Iron, it must be fused
with a certain quantity of Lead, and then the Copper, having a greater
affinity with Lead than with Iron, will desert the latter and join the
former, which being incapable of any union with Iron, as was said, will
wholly exclude it from the new compound. The next point is to separate
the Lead from the Copper; which is done by exposing the mass compounded
of these two metals to a degree of fire strong enough to deprive the
Lead of its metalline form, but too weak to have the same effect on
the Copper: and this may be done; since, of all the imperfect metals,
Lead is, next to Tin, the easiest to be calcined, and Copper on the
contrary resists the greatest force of fire longest, without losing its
metalline form. Now what we gain by this exchange, viz. by separating
Copper from Iron and uniting it with Lead, consists in this, that as
Lead is calcined with less fire than Iron, the Copper is less exposed
to be destroyed: for it must be observed that, however moderate the
fire be, it is hardly possible to prevent a certain quantity thereof
from being calcined in the operation.
Lead melted with a third part of Tin forms a compound, which being
exposed to a fire capable of making it thoroughly red-hot, swells,
puffs up, seems in some sort to take fire, and is presently calcined.
These two metals mixed together are much sooner calcined than either of
them separately.
Both Lead and Tin are in some measure affected by water, and by a moist
air; but they are both much less subject than Iron or Copper to be
corroded by these solvents, and of course are much less liable to rust.
The vitriolic acid acts upon and dissolves Lead, much in the same
manner as it doth Silver.
The nitrous acid dissolves this metal with much ease, and in great
quantities; and from this solution a small portion of Mercury may
be obtained. On this subject see our _Elements of the Practice of
Chymistry_.
When this solution of Lead is diluted with a good deal of water, the
Lead precipitates in the form of a white powder; which happens because
the acid is rendered too weak to keep the Lead dissolved.
If this solution of Lead be evaporated to a certain degree, it shoots
into crystals formed like regular pyramids with square bases. These
crystals are of a yellowish colour, and a saccharine taste: they do not
easily dissolve in water. This nitrous metalline salt has the singular
property of detonating in a crucible, without any additament, or the
contact of any other inflammable substance. This property it derives
from the great quantity of phlogiston contained in, and but loosely
connected with, the Lead which is one of its principles.
If spirit of salt, or even sea-salt in substance, be added to a
solution of Lead in the nitrous acid, a white precipitate immediately
falls; which is no other than the Lead united with the marine acid.
This precipitate is extremely like the precipitate of Silver made in
the same manner, and that being called _Luna cornea_ hath occasioned
this to be named _Plumbum corneum_. Like the _luna cornea_ it is
very fusible, and being melted hardens like it into a kind of horny
substance: it is volatile, and may be reduced by means of inflammable
matters combined with alkalis. But it differs from the _luna cornea_
in this chiefly, that it dissolves easily in water; whereas the _luna
cornea_, on the contrary, dissolves therein with great difficulty, and
in a very small quantity.
As this precipitation of Lead from its solution in spirit of nitre is
procured by the marine acid, Lead is thereby proved to have a greater
affinity with the latter acid than with the former. Yet, if you attempt
to dissolve Lead directly by the acid of sea-salt, the solution is
not so easily effected as by the spirit of nitre, and it is always
imperfect; for it wants one of the conditions essential to every
solution in a liquor, namely transparency.
If Lead be boiled for a long time in a lixivium of fixed alkali, part
of it will be dissolved.
Sulphur renders this metal refractory and scarce fusible; and the
mass they form when united together is friable. Hence it appears that
sulphur acts upon Lead much in the same manner as upon Tin; that is, it
renders both these metals less fusible, which are naturally the most
fusible of any, while it exceedingly facilitates the fusion of Silver,
Copper, and Iron, metals which of themselves flow with the greatest
difficulty.
CHAP. VIII.
_Of_ QUICK-SILVER.
We treat of Quick-silver in a chapter apart, because this metallic
substance cannot be classed with the metals properly so called, and
yet has some properties which will not allow us to confound it with
the semi-metals. The reason why Quick-silver, by the Chymists commonly
called Mercury, is not reputed a metal, is, that it wants one of the
essential properties thereof, to wit, malleability. When it is pure
and unadulterated with any mixture, it is always fluid, and of course
unmalleable. But as, on the other hand, it eminently possesses the
opacity, the splendour, and, above all, the gravity of a metal, being
next to Gold the heaviest of all bodies, it may be considered as a true
metal, differing from the rest no otherwise than by being constantly in
fusion; which we may suppose arises from its aptness to flow with such
a small degree of heat, that be there ever so little warmth on earth,
there is still more than enough to keep Mercury in fusion; which would
become solid and malleable if it were possible to apply to it a degree
of cold considerable enough for that purpose. These properties will not
allow us to confound it with the semi-metals. Add, that we are not yet
assured by any undoubted experiment that it can be wholly deprived of
its phlogiston, as the imperfect metals may. Indeed we cannot apply the
force of fire to it as could be wished: for it is so volatile that it
flies off and exhales in vapours, with a much less degree of fire than
is necessary to make it red-hot. The vapours of Mercury thus raised by
the action of fire, being collected and united in a certain quantity,
appear to be no other than true Mercury, retaining every one of its
properties; and no experiment hath ever been able to shew the least
change thus produced in its nature.
If Mercury be exposed to the greatest heat that it can bear without
sublimation, and continued in it for several months, or even a whole
year together, it turns to a red powder, which the Chymists call
_Mercurius Præcipitatus per se_. But, to succeed in this operation, it
is absolutely necessary that the heat be such as is above-specified;
for this metallic substance may remain exposed to a weaker heat for
a considerable number of years, without undergoing any sensible
alteration.
Some Chymists fancied, that by this operation they had fixed Mercury
and changed its nature; but without any reason: for if the Mercury
thus seemingly transmuted be exposed to a somewhat stronger degree of
fire, it sublimes and exhales in vapours as usual; and those vapours
collected are nothing else but running Mercury, which has recovered all
its properties without the help of any additament.
Mercury has the property of dissolving all the metals, Iron only
excepted. But it is a condition absolutely necessary to the success of
such dissolution, that the metalline substances be possessed of their
phlogiston; for if they be calcined, Mercury cannot touch them: and
hence it follows, that Mercury doth not unite with substances that are
purely earthy. Such a combination of a metal with Mercury is called an
_Amalgam_. Trituration alone is sufficient to effect it; however, a
proper degree of heat also is of use.
Mercury amalgamated with a metal gives it a consistence more or less
soft, and even fluid, according to the greater or smaller proportion of
Mercury employed. All amalgams are softened by heat, and hardened by
cold.
Mercury is very volatile; vastly more so than the most unfixed metals;
moreover, the union it contracts with any metal is not sufficiently
intimate to entitle the new compound resulting from that union to all
the properties of the two substances united: at least with regard to
their degree of fixity and volatility. From all which it follows, that
the best and surest method of separating it from metals dissolved by
it, is to expose the amalgam to a degree of heat sufficient to make
all the Quick-silver rise and evaporate; after which the metal remains
in the form of a powder, and being fused recovers its malleability.
If it be thought proper to save the Quick-silver, the operation must
be performed in close vessels, which will confine and collect the
mercurial vapours. This operation is most frequently employed to
separate Gold and Silver from the several sorts of earths and sands
with which they are mixed in the ore; because these two metals, Gold
especially, are of sufficient value to compensate the loss of Mercury,
which is inevitable in this process: besides, as they very readily
amalgamate with it, this way of separating them from every thing
unmetallic is very facile and commodious.
Mercury is dissolved by acids; but with circumstances peculiar to each
particular sort of acid.
The vitriolic acid, concentrated and made boiling hot, seizes on
it, and presently reduces it to a kind of white powder, which turns
yellow by the affusion of water, but does not dissolve in it; it is
called _Turbith Mineral_. However, the vitriolic acid on this occasion
unites with a great part of the Mercury, in such a manner that the
compound is soluble in water. For if to the water which was used to
wash the Turbith a fixed alkali be added, there falls instantly a
russet-coloured precipitate, which is no other than Mercury separated
from the vitriolic acid by the intervention of the alkali.
This dissolution of Mercury by the vitriolic acid is accompanied with
a very remarkable phenomenon; which is, that the acid contracts a
strong smell of volatile spirit of sulphur: a notable proof that part
of the phlogiston of the Mercury hath united therewith. And yet, if the
Mercury be separated by means of a fixed alkali, it does not appear to
have suffered any alteration. Turbith mineral is not so volatile as
pure Mercury.
The nitrous acid dissolves Mercury with ease. The solution is limpid
and transparent, and as it grows cold shoots into crystals, which are a
nitrous mercurial salt.
If this solution be evaporated to dryness, the Mercury remains
impregnated with a little of the acid, under the form of a red powder,
which hath obtained the names of _Red Precipitate_, and _Arcanum
Corallinum_. This Precipitate, as well as Turbith, is less volatile
than pure Mercury.
If this solution of Mercury be mixed with a solution of Copper, made
likewise in the nitrous acid, and the mixture evaporated to dryness,
there will remain a green powder called _Green Precipitate_. These
precipitates are caustic and corrosive; and are used as such in surgery.
Though Mercury be dissolved more easily and completely by the nitrous
acid than by the vitriolic, yet it has a greater affinity with the
latter than with the former: for if a vitriolic acid be poured into
a solution of Mercury in spirit of nitre, the Mercury will quit the
latter acid in which it was dissolved, and join the other which was
added. The same thing happens when the marine acid is employed instead
of the vitriolic.
Mercury combined with spirit of salt forms a singular body; a metalline
salt which shoots into long crystals, pointed like daggers. This
salt is volatile, and sublimes easily without decomposition. It is
moreover the most violent of all the corrosives hitherto discovered
by Chymistry. It is called _Corrosive Sublimate_, because it must
absolutely be sublimed to make the combination perfect. There are
several ways of doing this: but the operation will never fail, if the
Mercury be rarefied into vapours, and meet with the marine acid in a
similar state.
Corrosive Sublimate is dissolved by water, but in very small quantities
only. It is decompounded by fixed alkalis, which precipitate the
Mercury in a reddish yellow powder, called, on account of its colour,
_Yellow Precipitate_.
If Corrosive Sublimate be mixed with tin, and the compound distilled,
a liquor comes over which continually emits abundance of dense fumes,
and, from the name of its inventor, is called the _Smoking Liquor
of Libavius_. This liquor is no other than the tin combined with
the marine acid of the Corrosive Sublimate, which therefore it hath
actually decompounded: whence it follows, that this acid hath a greater
affinity with tin than with Mercury.
The marine acid in Corrosive Sublimate is not quite saturated with
Mercury; but is capable of taking up a much greater quantity thereof.
For if Corrosive Sublimate be mixed with fresh Mercury, and sublimed
a second time, another compound will be produced containing much more
Mercury, and less acrimonious; for which reason it is named _Sweet
Sublimate of Mercury_, _Mercurius dulcis_, _Aquila alba_. This compound
may be taken internally, and is purgative or emetic according to the
dose administered. It may be rendered still more gentle by repeated
sublimations, and then it takes the title of _Panacea Mercurialis_.
No way hath hitherto been found to dissolve Mercury in _aqua regis_
without great difficulty, and even then it is but imperfectly dissolved.
Mercury unites easily and intimately with sulphur. If these two
substances be only rubbed together in a gentle heat, or even without
any heat, they will contract an union, though but an incomplete one.
This combination takes the form of a black powder, which has procured
it the name of _Æthiops Mineral_.
If a more intimate and perfect union be desired, this compound must be
exposed to a stronger heat; and then a red ponderous substance will
be sublimed, appearing like a mass of shining needles: this is the
combination desired, and is called _Cinabar_. In this form chiefly
is Mercury found in the bowels of the earth. Cinabar finely levigated
acquires a much brighter red colour, and is known to painters by the
name of _Vermilion_.
Cinabar rises wholly by sublimation, without suffering any
decomposition; because the two substances of which it consists, _viz._
Mercury and Sulphur, are both volatile.
Though Mercury unites and combines very well with sulphur, as hath
been said, yet it hath less affinity with that mineral than any other
metal, Gold only excepted: whence it follows, that any of the other
metals will decompound Cinabar, by uniting with its sulphur, and so
setting the Mercury at liberty to appear in its usual form. Mercury
thus separated from sulphur is esteemed the purest, and bears the name
of _Mercury revivified from Cinabar_.
Iron is generally used in this operation, preferably to the other
metals, because among them all it has the greatest affinity with
sulphur, and is the only one that has none with Mercury.
Cinabar may also be decompounded by means of fixed alkalis; the
affinity of these salts with sulphur being generally greater than that
of any metalline substance whatever.
CHAP. IX.
_Of the_ SEMI-METALS.
SECTION I.
_Of_ REGULUS OF ANTIMONY.
Regulus of Antimony is a metallic substance of a pretty bright white
colour. It has the splendour, opacity, and gravity of a metal: but it
is quite unmalleable, and crumbles to dust, instead of yielding or
stretching, under the hammer; on which account it is classed with the
Semi-metals.
It begins to flow as soon as it is moderately red; but, like the other
Semi-metals, it cannot stand a violent degree of fire; being thereby
dissipated into smoke and white vapours, which adhere to such cold
bodies as they meet with, and so are collected into a kind of _farina_
called _Flowers of Antimony_.
If Regulus of Antimony, instead of being exposed to a strong fire, be
only heated so moderately that it shall not even melt, it will calcine,
lose its phlogiston, and take the form of a greyish powder destitute of
all splendour: this powder is called _Calx of Antimony_.
This calx is not volatile like the Regulus, but will endure a very
violent fire; and being exposed thereto will flow, and turn to a glass
of the yellowish colour of a hyacinth.
It is to be observed, that the more the Regulus is deprived of its
phlogiston by continued calcination, the more refractory is the calx
obtained from it. The glass thereof has also so much the less colour,
and comes the nearer to common glass.
The calx and the Glass of Antimony will recover their metalline form,
like every other Calx and Glass of a metal, if reduced by restoring to
them their lost phlogiston. Yet if the calcination be carried too far,
their reduction will become much more difficult, and a much smaller
quantity of Regulus will be resuscitated.
Regulus of Antimony is capable of dissolving the metals: but its
affinities with them are various, and differ according to the following
order. It affects Iron the most powerfully, next Copper, then Tin,
Lead, and Silver. It promotes the fusion of metals, but makes them all
brittle and unmalleable.
It will not amalgamate with Mercury; and though by certain processes,
particularly the addition of water and continued trituration, a sort
of union between these two substances may be produced, yet it is but
apparent and momentary; for, being left to themselves and undisturbed,
they quickly disunite and separate[2].
[2] M. Malouin, however, hath found a way to unite these two metallic
substances: but then he does it by the interposition of sulphur; that
is, he combines crude Antimony with Mercury. This combination is
brought about in the same way that Æthiops Mineral is made; _viz._
either by fusion, or by trituration only without fire. It resembles
the common Æthiops, and M. Malouin calls it _Æthiops of Antimony_. He
observed that Mercury unites with Antimony much more intimately, by
melting, than by rubbing them together.
The vitriolic acid, assisted by heat, and even by distillation,
dissolves Regulus of Antimony. The nitrous acid likewise attacks it:
but the solution can by no art be made clear and limpid: so that the
Regulus is only calcined, in a manner, by this acid.
The marine acid dissolves it well enough; but then it must be
exceedingly concentrated, and applied in a peculiar manner, and
especially by distillation. One of the best methods of procuring a
perfect union between the acid of sea-salt and Regulus of Antimony, is
to pulverize the latter, mix it with corrosive sublimate, and distil
the whole. There rises in the operation a white matter, thick, and
scarce fluid, which is no other than the Regulus of Antimony united
and combined with the acid of sea-salt. This compound is extremely
corrosive, and is called _Butter of Antimony_.
It is plain that the corrosive sublimate is here decompounded; that the
Mercury is revivified, and that the acid which was combined therewith
hath quitted it to join the Regulus of Antimony, with which its
affinity is greater. This Butter of Antimony by repeated distillations
acquires a considerable degree of fluidity and limpidness.
If the acid of nitre be mixed with Butter of Antimony, and the whole
distilled, there rises an acid liquor, or a sort of _aqua regis_, which
still retains some of the dissolved Regulus, and is called _Bezoardic
Spirit of Nitre_. After the distillation there remains a white matter,
from which fresh spirit of nitre is again abstracted, and which being
then washed with water is called _Bezoar Mineral_. This Bezoar Mineral
is neither so volatile nor so caustic as Butter of Antimony; because
the nitrous acid hath not the property of volatilizing metallic
substances, as the marine acid does, and because it remains much more
intimately combined with the reguline part.
If Butter of Antimony be mixed with water, the liquor immediately
becomes turbid and milky, and a precipitate falls, which is nothing
but the metallic matter partly separated from its acid, which is too
much weakened by the addition of water to keep it dissolved. Yet this
precipitate still retains a good deal of acid; for which reason it
continues to be a violent emetic, and in some degree corrosive. It hath
therefore been very improperly called _Mercurius Vitæ_.
The proper solvent of Regulus of Antimony is _aqua regis_; by means
whereof a clear and limpid solution of this Semi-metal may be obtained.
Regulus of Antimony mixed with nitre, and projected into a red-hot
crucible, sets the nitre in a flame, and makes it detonate. As it
produces this effect by means of its phlogiston, it must needs at
the same time be calcined, and lose its metallic properties, which
accordingly happens, and when the nitre is in a triple proportion to
the Regulus, the latter is so perfectly calcined as to leave only a
white powder, which is fused with great difficulty, and then turns to a
faintly coloured glass, not very different from common glass, and which
is not reducible to a Regulus by the addition of inflammable matter;
at least it yields but a very small quantity thereof. If less nitre be
used, the calx is not so white; the glass it produces is more like a
metalline glass, and is more easily reduced. The calx of the Regulus
thus prepared by nitre is called, on account of the medicinal virtue
ascribed to it, _Diaphoretic Antimony_, or _Diaphoretic Mineral_.
Nitre always becomes an alkali by deflagration, and in the present
case retains part of the calx, which it even renders soluble in water.
This calx may be separated from the alkali, if an acid be employed to
precipitate it; and then it is called _Materia Perlata_. This pearly
matter is a calx of Antimony, so completely deprived of its phlogiston
as to be altogether incapable of reduction to a Regulus.
Regulus of Antimony readily joins and unites with sulphur, forming
therewith a compound which has a very faint metallic splendour.
This compound appears like a mass of long needles adhering together
laterally; and under this form it is usually found in the ore, or at
least when only separated by fusion from the stones and earthy matters
with which the ore is mixed. It is called _Crude Antimony_.
Antimony flows with a moderate heat, and becomes even more fluid than
other metallic substances. The action of fire dissipates or consumes
the sulphur it contains, and its phlogiston also, so as to convert it
into a calx and a glass, as it does the Regulus.
_Aqua regis_, which we observed to be the proper solvent of the
Regulus, being poured on Antimony, attacks and dissolves the reguline
part, but touches not the sulphur; in consequence whereof it decomposes
the Antimony, and separates its sulphur from its Regulus.
There are several other ways of effecting this decomposition, and
obtaining the reguline part of Antimony by itself: they consist either
in destroying the sulphureous part of the Antimony by combustion, or in
melting the Antimony with some substance which has a greater affinity
than its reguline part with sulphur. Most metals are very fit for this
latter purpose: for though the Regulus has a considerable affinity with
sulphur, yet all the metals, except Gold and Mercury, have a greater.
If therefore Iron, Copper, Lead, Silver, or Tin, be melted with
Antimony, the metal employed will unite with the sulphur, and separate
it from the Regulus.
It must be observed, that, as these metals have some affinity with the
Regulus of Antimony, the Regulus will be joined in the operation by
some of the metal employed as a _Precipitant_, (so those substances
are called which serve as the means of separating two bodies from each
other); and therefore the Regulus procured in this manner will not be
absolutely pure: on this account care is taken to distinguish each by
adding the name of the metal employed in its precipitation; and thence
come these titles, _Martial Regulus of Antimony_, or only _Martial
Regulus_, _Regulus Veneris_; and so of the rest.
Antimony is employed with advantage to separate Gold from all the
other metals with which it may be alloyed. It has been shewn, that all
the metals have a greater affinity than the reguline part of Antimony
with sulphur, Gold only excepted; which is incapable of contracting
any union therewith: and therefore, if a mass compounded of Gold and
several other metals be melted with Antimony, every thing in that
mass which is not Gold will unite with the sulphur of the Antimony.
This union occasions two separations, to wit, that of the sulphur
of the Antimony from its reguline part, and that of the Gold from
the metals with which it was adulterated; and from the whole two new
compounds arise; namely, a combination of the metals with the sulphur,
which being lightest rises to the surface in fusion; and a metalline
mass, formed of the Gold and the reguline part of the Antimony united
together, which being much the heaviest sinks to the bottom. There is
no difficulty in parting the Gold from the Regulus of Antimony with
which it is alloyed: for the metalline mass needs only be exposed to a
degree of fire capable of dissipating into vapours all the Semi-metal
it contains; which being very volatile, the operation is much easier,
and more expeditiously finished, than if the metals with which the Gold
was debased were to be vitrified on the cupel; without taking into the
account, that, if Silver were one of them, recourse must needs be had
to the process of quartation after that of the cupel.
If equal parts of nitre and Antimony be mixed together, and the mixture
exposed to the action of fire, a violent detonation ensues; the nitre
deflagrating consumes the sulphur of the Antimony, and even a part of
its phlogiston. After the detonation there remains a greyish matter
which contains fixed nitre, vitriolated tartar, and the reguline part
of the Antimony in some measure deprived of its phlogiston, and half
vitrified by the action of the fire, which is considerably increased by
the deflagration. This matter is called _Liver of Antimony_.
If, instead of equal parts of nitre and Antimony, two parts of the
former be used to one of the latter, then the reguline part loses much
more of its phlogiston, and remains in the form of a yellowish powder.
Again, if three parts of nitre be taken to one of Antimony, the Regulus
is thereby entirely robbed of its phlogiston, and converted to a white
calx, which bears the name of _Diaphoretic Antimony_, or _Diaphoretic
Mineral_. The pearly matter may be precipitated by pouring an acid
on the saline substances which here remain after the detonation, in
the same manner as we shewed above was to be done with regard to the
Regulus.
In the two last operations, where the nitre is in a double or triple
proportion to the Antimony, the reguline part is found after the
detonation to be converted into a calx, and not into a half-vitrified
matter, which we have seen is the effect when equal parts only of nitre
and Antimony are used. The reason of this difference is, that in these
two cases the reguline part, being wholly, or almost wholly, deprived
of its phlogiston, becomes, as was observed, more difficult to fuse,
and consequently cannot begin to vitrify in the same degree of heat
as that which hath not lost so much of its phlogiston. If, instead of
performing the operation with equal parts of nitre and Antimony alone,
a portion of some substance which abounds with phlogiston be added, in
that case the sulphur only of the Antimony will be consumed, and the
Regulus will remain united with its phlogiston and separated from its
sulphur.
The Regulus prepared in this manner is absolutely pure, because no
metalline substance being employed, none can mix with and adulterate
it. It is called _Regulus of Antimony per se_, or only _Regulus of
Antimony_.
It is true indeed that in this operation much of the reguline part
unavoidably loses its phlogiston and is calcined, and consequently
a much smaller quantity of Regulus is obtained than when metalline
precipitants are employed: but this loss is easily repaired, if it be
thought proper, by restoring to the calcined part its lost phlogiston.
Antimony melted with two parts of fixed alkali yields no Regulus,
but is entirely dissolved by the salt, and forms with it a mass of a
reddish yellow colour.
The reason why no precipitate is produced on this occasion is, that the
alkali uniting with the sulphur of the Antimony forms therewith the
combination called Liver of Sulphur, which by its nature is qualified
to keep the reguline part dissolved. This mass formed by the union of
the Antimony with the alkali is soluble in water. If any acid whatever
be dropt into this solution, there falls a precipitate of a reddish
yellow colour; because the acid unites with the alkali, and forces it
to quit the matters with which it was combined. This precipitate is
called _Golden Sulphur of Antimony_.
As in the operation for preparing _Regulus of Antimony per se_, some of
the nitre is, by the inflammable matters added thereto, turned to an
alkali, this alkali seizes on part of the Antimony, and therewith forms
a compound like that just described. Hence it comes, that if the scoria
formed in this process be dissolved in water, and an acid dropped into
the solution, a true golden sulphur of Antimony is thereby separated.
This union of Antimony with an alkali may also be brought about by the
humid way; that is, by making use of an alkali resolved into a liquor,
and boiling the mineral in it. The alkaline liquor, in proportion as
it acts upon the Antimony, gradually becomes reddish and turbid. If
left to settle and cool when well saturated therewith, it gradually
deposites the Antimony it had taken up, which precipitates in the form
of a red powder; and this precipitate is the celebrated remedy known
by the name of _Kermes Mineral_. It is plain that the kermes is nearly
the same thing with the golden sulphur: yet it differs from it in some
respects; and especially in this, that being taken inwardly it operates
much more gently than the golden sulphur, which is a violent emetic.
Nitre fixed by charcoal, and resolved into a liquor, is the only alkali
employed in preparing the kermes.
It was shewn above, that Regulus of Antimony mixed and distilled with
corrosive sublimate decompounds it, disengages the Mercury, and joining
itself to the marine acid forms therewith a new combination, called
Butter of Antimony. If the same operation be performed with crude
Antimony instead of its Regulus, the same effects are produced: but
then the Antimony itself is also decomposed; that is, the reguline
part is separated from the sulphur, which being set free unites with
the Mercury, now also at liberty, and these two together form a true
cinabar, called _Cinabar of Antimony_.
SECTION II.
_Of_ BISMUTH.
Bismuth, known also by the name of Tin-glass, is a semi-metal, having
almost the same appearance as Regulus of Antimony; yet it has a
more dusky cast, inclining somewhat to red, and even presents some
changeable streaks, especially after lying long in the air.
When exposed to the fire it melts long before it is red, and
consequently with less heat than Regulus of Antimony, which does not
flow, as was shewn above, till it begin to be red-hot. It becomes
volatile, like all the other semi-metals, when acted on by a violent
fire: being kept in fusion by a proper degree of heat it loses its
phlogiston with its metallic form, and turns to a powder or a calx; and
that again is converted into glass by the continued action of fire. The
calx and glass of Bismuth may be reduced, like any other metallic calx,
by restoring their phlogiston.
Bismuth mixes with all the metals in fusion, and even facilitates the
fusion of such as do not otherwise flow readily. It whitens them by its
union, and destroys their malleability.
It amalgamates with Mercury, if they be rubbed together with the
addition of water: yet after some time these two metalline substances
desert each other, and the Bismuth appears again in the form of a
powder. Hence it is plain, that the union it contracts with Mercury is
not perfect; and yet it has the singular property of attenuating Lead,
and altering it in such a manner that it afterwards amalgamates with
Mercury much more perfectly, so as even to pass with it through shamoy
leather without any separation. The Bismuth employed in making this
amalgama afterwards separates from it spontaneously, as usual; but the
Lead still continues united with the Mercury, and always retains the
property thus acquired.
The vitriolic acid does not dissolve Bismuth: its proper solvent is the
nitrous acid, which dissolves it with violence, and abundance of fumes.
Bismuth dissolved in the nitrous acid is precipitated not only by
alkalis, but even by the bare addition of water. This precipitate is
extremely white, and known by the name of _Magistery of Bismuth_.
The acid of sea-salt and _aqua regis_ likewise act upon Bismuth, but
with less violence.
This semi-metal does not sensibly deflagrate with nitre; yet it is
quickly deprived of its phlogiston, and turned into a vitrifiable calx,
when exposed with it to the action of fire.
It readily unites with sulphur in fusion, and forms therewith a
compound which appears to consist of needles adhering laterally to each
other.
It may be separated from the sulphur with which is combined, by only
exposing it to the fire, without any additament; for the sulphur is
either consumed or sublimed, and leaves the Bismuth behind.
SECTION III.
_Of_ ZINC.
Zinc to appearance differs but little from Bismuth, and has even been
confounded with it by several authors. Nevertheless, besides that it
has something of a blueish cast, and is harder than Bismuth, it differs
from it essentially in its properties, as will presently be shewn.
These two metallic substances scarce resemble each other in any thing,
but the qualities common to all semi-metals.
Zinc melts the moment it grows red in the fire, and then also begins
to turn to a calx, which, like any other metallic calx, may be reduced
by means of the phlogiston: but if the fire be considerably increased,
it sublimes, flames, and burns like an oily matter; which is a proof
of the great quantity of phlogiston in its composition. At the same
time abundance of flowers rise from it in the form of white flakes,
flying about in the air like very light bodies; and into this form
may the whole substance of the Zinc be converted. Several names have
been given to these flowers, such as Pompholyx, Philosophic Wool.
They are supposed to be no other than the Zinc itself deprived of its
phlogiston; yet no body has hitherto been able to resuscitate them
in the form of Zinc, by restoring their phlogiston according to the
methods used in the reduction of metals. Though they rise in the air
with very great ease while the Zinc is calcining, yet when once formed
they are very fixed; for they withstand the utmost violence of fire,
and are capable of being vitrified, especially if joined with a fixed
alkali. They are soluble in acids.
Zinc unites with all metalline substances, except Bismuth. It has
this singular property, that being mixed with Copper, even in a
considerable quantity, such as a fourth part, it does not greatly
lessen the ductility thereof, and at the same time communicates to it
a very beautiful colour not unlike that of Gold: on which account the
composition is frequently made, and produces what is called _Brass_.
This metal melts much more easily than Copper alone, because of the
Zinc with which it is alloyed. If it be exposed to a great degree of
heat, the Zinc which it contains takes fire, and sublimes in white
flowers, just as when it is pure.
It is to be observed, that Brass is ductile only while it is cold, and
not then, unless the Zinc used in making it was very pure; otherwise
the composition will prove but a _Tombac_ or _Prince's Metal_, having
very little malleability.
Zinc is very volatile, and carries off with it any metallic substance
with which it is fused, making a kind of sublimate thereof. In the
furnaces where they smelt ores containing Zinc, the matter thus
sublimed is called _Cadmia Fornacum_, to distinguish it from the
native _Cadmia_ called also _Calamine_, or _Lapis Calaminaris_; which,
properly speaking, is an ore of Zinc, containing a great deal of that
semi-metal, together with some Iron, and a stony substance. The name of
_Cadmia Fornacum_ is not appropriated solely to the metallic sublimates
procured by means of Zinc, but is given in general to all the metallic
sublimates found in smelting houses.
If a violent and sudden heat be applied to Zinc, it sublimes in its
metalline form; there not being time for it to burn and be resolved
into flowers.
This semi-metal is soluble in all the acids, but especially in spirit
of nitre, which attacks and dissolves it with very great violence.
Zinc has a greater affinity than iron or copper with the vitriolic
acid; and therefore it decompounds the green and blue vitriols,
precipitating those two metals by uniting with the vitriolic acid, with
which it forms a metallic salt, or vitriol, called _White Vitriol_, or
_Vitriol of Zinc_.
Nitre mixed with Zinc, and projected into a red-hot crucible, detonates
with violence, and during the detonation there rises a great quantity
of white flowers, like those which appear when it is calcined by itself.
Sulphur has no power over Zinc. Even liver of sulphur, which dissolves
all other metallic substances, contracts no union with this semi-metal.
Messrs. Hellot and Malouin have bestowed a great deal of pains on this
semi-metal. An account of their experiments is to be found in the
Memoirs of the Academy of Sciences.
SECTION IV.
_Of_ REGULUS OF ARSENIC.
Regulus of Arsenic is the most volatile of all the semi-metals. A very
moderate heat makes it wholly evaporate, and fly off in fumes; on which
account it cannot be brought to fusion, nor can any considerable masses
thereof be obtained. It has a metallic colour, somewhat resembling
Lead; but it soon loses its splendour when exposed to the air.
It unites readily enough with metallic substances, having the same
affinities with them as Regulus of Antimony hath. It makes them
brittle, and unmalleable. It hath also the property of rendering them
volatile, and greatly facilitates their scorification.
It very easily parts with its phlogiston and its metallic form. When
exposed to the fire it rises in a kind of shining crystalline calx,
which, on that account, looks more like a saline matter than a metallic
calx. To this calx or these flowers are given the names of _White
Arsenic_, _Crystalline Arsenic_, and most commonly plain _Arsenic_.
The properties of this substance are very singular, and extremely
different from those of any other metallic calx. Hitherto it hath been
but little examined; and this led me to make some attempts towards
discovering its nature, which may be seen in the Memoirs of the Academy
of Sciences.
Arsenic differs from every other metalline calx, first, in being
volatile; whereas the calces of all other metallic substances, not
excepting those of the most volatile semi-metals, such as Regulus of
Antimony and Zinc, are exceeding fixed; and, secondly, in having a
saline character, which is not found in any other metalline calx.
The saline character of Arsenic appears, first, from its being soluble
in water; secondly, from its corrosive quality, which makes it one
of the most violent poisons: a quality from which the other metallic
substances are free, when they are not combined with some saline
matter. Regulus of Antimony must however be excepted. But then the
best Chymists agree that this semi-metal is either nearly of the same
nature with Arsenic, or contains a portion thereof in its composition:
besides, its noxious qualities never discover themselves so plainly
as when it is combined with some acid. Lastly, Arsenic acts just like
the vitriolic acid upon nitre; that is, it decompounds that neutral
salt, by expelling its acid from its alkaline basis, of which it takes
possession, and therewith forms a new saline compound.
This combination is a species of salt that is perfectly neutral. When
the operation is performed in a close vessel, the salt shoots into
crystals in the form of right-angled quadrangular prisms, terminated at
each extremity by pyramids that are also quadrangular and right angled;
some of which however, instead of ending in a point, are obtuse as if
truncated. The consequence is different when the operation is performed
in an open vessel; for then nothing is obtained but an alkaline salt
impregnated with Arsenic, which cannot be crystallized.
The cause of this different effect is, that, when the Arsenic is once
engaged in the alkaline basis of the nitre, it can never be separated
from it by the utmost force of fire, so long as it is kept in a close
vessel; whereas, if you expose it to the fire without that precaution,
it readily separates from it. This property of arsenic was never before
observed by any Chymist, and therefore this our new species of Neutral
arsenical salt was absolutely unknown till lately.
This new salt possesses many singular properties, the chief of which
are these. First, it cannot be decompounded by the intervention of
any acid, even the strongest acid of vitriol; and this, joined to its
property of expelling the nitrous acid from its basis, shews that it
has a very great affinity with fixed alkalis.
Secondly, this very salt, on which pure acids have no effect, is
decompounded with the greatest ease by acids united with metallic
substances. The reason of this phenomenon is curious, and furnishes us
with an instance of what we advanced concerning double affinities.
If to a resolution of any metallic substance whatever, made by any acid
whatever, (except that of Mercury by the marine acid, and that of Gold
by _aqua regis_), a certain quantity of our New Salt dissolved in water
be added, the metallic substance is instantaneously separated from the
acid in which it was dissolved, and falls to the bottom of the liquor.
All metallic precipitates obtained in this manner are found to be a
combination of the metal with Arsenic; whence it necessarily follows
that the new Neutral Salt is by this means decompounded, its arsenical
part uniting with the metallic substance, and its alkaline basis with
the acid in which that substance was dissolved.
The affinities of these several bodies must be considered as operating
on this occasion in the following manner: The acids which tend to
decompound the Neutral Salt of Arsenic, by virtue of their affinity
with its alkaline basis, are not able to accomplish it, because this
affinity is powerfully counteracted by that which the Arsenic has with
the same alkaline basis, and which is equal or even superior to theirs.
But if these acids happen to be united with a substance which naturally
has a very great affinity with the arsenical part of the Neutral Salt,
then, the two parts of which this Salt consists being drawn different
ways by two several affinities tending to separate them from each
other, the Salt will undergo a decomposition, which could not have been
effected without the help of this second affinity. Now, as metallic
substances have a great affinity with Arsenic, it is not surprising
that the Neutral Salt of Arsenic, which cannot be decompounded by a
pure acid, should nevertheless yield to an acid combined with a metal.
The decomposition of this Salt, therefore, and the precipitation which
of course it produces in metallic solutions, are brought about by the
means of a double affinity; namely, that of the acid with the alkaline
basis of the Neutral Salt, and that of the metal with the arsenical
part of that salt.
Arsenic has not the same effect on sea-salt as on nitre, and cannot
expel its acid: a very singular phenomenon, for which it is hard to
assign a reason; for the nitrous acid is known to have a greater
affinity than the marine acid with alkalis, and even with the basis of
sea-salt itself.
Yet Arsenic may be combined with the basis of sea-salt, and a Neutral
Salt thereby obtained, like that which results from the decomposition
of nitre by Arsenic: but for that purpose a quadrangular nitre must be
first prepared, and Arsenic applied thereto as to common nitre.
The Salt produced by uniting Arsenic with the basis of sea-salt very
much resembles the Neutral Salt of Arsenic above treated of as well in
the figure of its crystals as in its several properties.
Arsenic presents another singular phenomenon, both with the alkali of
nitre and with that of sea-salt; which is, that if it be combined with
these salts in a fluid state, it forms with them a saline compound,
quite different from the Neutral Salts of Arsenic which result from the
decomposition of nitrous salts.
This saline compound, which I call _Liver of Arsenic_, takes up a
much greater quantity of Arsenic than is necessary for the perfect
saturation of the alkali. It has the appearance of a glue, which
is so much the thicker the more Arsenic it contains. Its smell is
disagreeable; it attracts the moisture of the air, and does not
crystallize; it is easily decompounded by any acid whatever, which
precipitates the Arsenic and unites with the alkali. Lastly, the
effects it produces on metallic solutions are different from those of
our neutral arsenical salts. But the bounds which I have set myself
in this treatise will not allow me to be more particular. Such as
have the curiosity to inquire further into the subject may consult my
Dissertations on Arsenic, published among the Memoirs of the Academy of
Sciences.
Arsenic is easily reduced to a Regulus. It need only be mixed with any
matter containing the phlogiston, and by the help of a moderate heat a
true Regulus will sublime. This Regulus, as was said, is very volatile,
and calcines with the greatest ease; which is the reason why it cannot
be obtained but in small quantities, and also why, in order to obtain
masses of it, some have thought of adding thereto some metal with which
it has a great affinity, such as Copper or Iron; because, by joining
with the metal, it is partly fixed and restrained from flying off. But
it is plain the Regulus obtained by this means is not pure, as it must
partake considerably of the metal employed.
Arsenic readily unites with sulphur, and rises with it in a yellow
compound, called _Orpiment_.
Sulphur cannot be separated from Arsenic but by the intervention of two
bodies only; to wit, a fixed alkali and Mercury.
The property which Mercury possesses of separating sulphur from Arsenic
is founded on this, that these two metallic substances are incapable
of contracting any union; whereas, though most of the other metals and
semi-metals have a greater affinity with sulphur than Mercury hath, as
was shewn in treating of the decomposition of Cinabar, nevertheless
they are all unable to decompound Orpiment; because some of them have
as great an affinity with Arsenic as with sulphur; others have no
affinity with either; and lastly, sulphur hath as great an affinity
with Arsenic as with any of them.
It must be observed that, if fixed alkalis be employed to purify
Arsenic in this manner, no more must be used than is necessary to
absorb the sulphur or the phlogiston, of which also it is their nature
to deprive Arsenic; for otherwise, as it has been shewn that Arsenic
readily unites with alkalis, they would absorb a considerable quantity
thereof.
CHAP. X.
_Of_ OIL _in general_.
Oil is an unctuous body, which burns and consumes with flame and smoke,
and is not soluble in water. It consists of the phlogiston united with
water by means of an acid. There is, moreover, in its composition a
certain proportion of earth, more or less, according to each several
sort of Oil.
The inflammability of Oil evidently proves that it contains the
phlogiston. That an acid is one of its constituent principles many
experiments demonstrate, of which these are the chief: If certain Oils
be long triturated with an alkaline salt, and the alkali afterwards
dissolved in water, crystals of a true neutral salt will be produced:
some metals, and particularly Copper, are corroded and rusted by Oils,
just as they are by acids: again, acid crystals are found in some Oils
that have been long kept. This acid in Oil serves undoubtedly to unite
its phlogiston with its water; because these two substances having no
affinity with each other cannot be united without the intervention of
such a medium as an acid, which has an affinity with both. As to the
existence of water in Oils, it appears plainly when they are decomposed
by repeated distillations, especially after mixing them with absorbent
earths. Lastly, when an Oil is destroyed by burning, a certain quantity
of earth is constantly left behind.
We are very sure that the above-mentioned principles enter into the
composition of Oils; for they may be obtained from every one of them:
but it is not absolutely certain that they consist of these only, and
that they do not contain some other principle which may escape our
notice in decomposing them; for hitherto it doth not appear, by any
experiment we can depend on, that Oil was ever produced by combining
together the principles here specified: yet such redintegrations are
the only means we have of satisfying ourselves that we know all the
principles which constitute a body.
Oils exposed to the fire in close vessels pass over almost wholly from
the containing vessel into any other applied to receive them. There
remains, however, a small quantity of black matter, which is extremely
fixed, and continues unalterable as long as it hath no communication
with the external air, be the force of the fire ever so violent. This
matter is no other than part of the phlogiston of the Oil united
with its most fixed and grossest earth; and this is what we called
_Charcoal_, or plainly a _Coal_.
SECTION I.
_Of_ CHARCOAL.
When Oil happens to be united to much earth, as it is in vegetable and
animal bodies, it leaves a considerable quantity of _Coal_ or charred
matter.
This Coal, exposed to the fire in the open air, burns and wastes,
but without blazing like other combustible matters: there appears
only a small blueish flame, but not the least smoke. Most commonly
it only glows and sparkles, and so gradually falls into ashes, which
are nothing but the earth of the body, combined with an alkaline salt
in burning. This alkaline salt may be separated from the earth, by
lixiviating the ashes with water, which dissolves all the salt, and
leaves the earth quite pure.
Charcoal is unalterable and indestructible by any other body but fire;
whence it follows, that when it is not actually kindled and ignited,
the most powerful agents, such as the acids, though ever so strong and
concentrated, have not the least effect on it.
The case is otherwise when it is lighted, that is, when its phlogiston
begins to separate from its earth; for then the pure acid of vitriol
being joined therewith, contracts an instantaneous union with its
phlogiston, and evaporates in a volatile sulphureous spirit. If the
vitriolic acid, instead of being applied quite pure, be first clogged
with some basis, especially an alkaline one, it quits that basis,
enters into a more intimate union with the phlogiston of the burning
Coal, and so forms an actual sulphur, with which the alkali now unites
and forms a hepar.
The pure acid of sea-salt hath not been observed to act in the least
upon Charcoal, especially when it is not on fire. But when this acid
is incorporated with an alkaline or metallic basis, and combined
according to a peculiar process with burning Charcoal, it in like
manner quits its basis, unites with the phlogiston, and therewith forms
a phosphorus, of which we have already taken notice.
Nor has the pure nitrous acid any effect on a charred Coal, even when
ignited: and so far is it from being able to kindle a cold one, that
when poured on a live one, it extinguishes it like water. But when
this acid is united with a basis, it quits it rapidly as soon as it
touches a burning coal, and rushes violently into an union with the
phlogiston thereof. From this union there probably arises, as we said
before, a kind of sulphur or phosphorus, which is so inflammable as to
be destroyed by the fire the very moment it is generated.
The acids of nitre and vitriol act upon Oils; but very differently,
according to the quantity of phlegm they contain. If they be weakened
with much water, they have no effect at all upon Oils; if they contain
little water, or be dephlegmated to a certain degree, they dissolve
them with heat, and with them form compounds of a thick consistence.
Acids, thus combined in a considerable proportion with Oils, render
them soluble in water.
SECTION II.
_Of_ SOAP.
Alkalis also have the same property. When an Oil is combined with an
acid or an alkali in such a manner, that the compound resulting from
their union is soluble in water; such a compound may in general be
called a _Soap_. Soap itself hath the property of rendering fat bodies
in some measure soluble in water; on which account it is very useful
for scouring or cleansing any thing greasy.
Oily and saline substances, combined together, observe the same general
rules as all other combinations; that is, they mutually communicate
the properties belonging to each: thus Oils, which naturally are not
soluble in water, acquire, by their union with saline matters, the
property of dissolving therein; and salts lose, by their conjunction
with Oils, part of their natural tendency to incorporate with water;
so that, while they serve to constitute soap, they do not, as before,
attract the moisture of the air, _&c._ and, in like manner, as they are
not inflammable, they considerably lessen the inflammability of the
Oils combined with them.
Acid Soaps are decompounded by alkalis, as alkaline Soaps are by acids,
according to the general rules of affinities.
The acids of nitre and vitriol, when highly concentrated, dissolve
Oils with such violence as to heat them, make them black, burn them,
and even set them on fire. How sea-salt affects Oils is not yet
sufficiently ascertained.
All Oils have the property of dissolving sulphur; which is not at all
surprising, seeing each of its component principles hath an affinity
with Oil.
It is also a property common to all Oils to become more fluid, subtile,
light, and limpid, the oftener they are distilled. On the contrary,
by being incorporated with saline substances they acquire a greater
consistence, and sometimes form compounds that are most solid.
CHAP. XI.
_Of the several Sorts of_ OILS.
Oils are distinguished by the substances from which they are drawn: and
as Oils are extracted from minerals, from vegetables, and from animals,
there are of course Mineral, Vegetable, and Animal Oils.
SECTION I.
_Of_ MINERAL OILS.
In the bowels of the earth we find but one sort of Oil, called
_Petroleum_: its smell is strong and not disagreeable, and its colour
sometimes more sometimes less yellow. There are certain mineral
substances which yield by distillation a great deal of Oil very like
Petroleum. This sort of substance is called a _Bitumen_, and is,
indeed, nothing but an Oil rendered consistent and solid by being
combined with an acid; as appears from hence, that by uniting Petroleum
with the acid of vitriol we can produce an artificial Bitumen very like
the native.
SECTION II.
_Of_ VEGETABLE OILS.
Vegetable substances yield a very great quantity and variety of oils:
for there is not a plant, or part of a plant, that does not contain one
or more sorts thereof, generally peculiar to itself, and different from
all others.
By expression only, that is, by bruising and squeezing vegetable
substances, particularly certain fruits and seeds, a sort of oil is
obtained which has scarce any smell or taste. Oils of this sort are
very mild and unctuous; and, because in this respect they resemble
animal fat more than the rest do, they are called _Fat Oils_.
These Oils, being exposed to the air for some time, sooner or latter
grow thick, acquire an acrid taste, and a strong disagreeable smell.
Some of them congeal with the smallest degree of cold. This sort of
Oil is well adapted to dissolve those preparations of Lead called
Litharge and Minium, with which they form a thick tenacious substance,
that is used for the basis of almost all plasters. They also dissolve
Lead in its metalline form; but not so easily as the sorts of calx
above-mentioned; probably because its body is not so much opened, nor
its parts so divided.
By expression alone we also procure from certain vegetable substances
another sort of Oil, which is thin, limpid, volatile, of a pungent
taste, and retains the smell of the vegetable that yielded it; on which
account it is called an _Essential Oil_. Of this there are several
sorts, differing from one another, like the Fat Oils, according to the
subjects from which they are obtained.
We must observe, that it is very difficult, or rather in most
cases impossible, to force from the greatest part of vegetables,
by expression only, all the essential Oil they contain. For this
purpose therefore recourse must be had to fire: a gentle heat, not
exceeding that of boiling water, will extract all the essential Oils
of vegetables; and this is the most usual and most convenient way of
procuring them.
The fat Oils cannot be obtained by the same method: these being much
less volatile than the essential Oils, require a much greater degree of
heat to raise them; which nevertheless they cannot bear without being
much spoiled and entirely changed in their nature, as shall presently
be shewn. All Oils, therefore, which rise with the heat of boiling
water, and such alone, should be called Essential Oils.
Essential Oils, in a longer or shorter time, according to the nature
of each, lose the fragrant smell they had when newly distilled, and
acquire another, which is strong, rancid, and much less agreeable: they
also lose their tenuity, becoming thick and viscid; and in this state
they greatly resemble those substances abounding in Oil which flow from
certain trees, and which are called _Balsams_ or _Resins_, according as
they are less or more consistent.
Balsams and Resins are not soluble in water. But there are other Oily
compounds which likewise run from trees; and, though not unlike Resins,
are however soluble in water. These are called _Gums_; and their
property of dissolving in water arises from their containing more water
and more salt than Resins have; or at least their saline parts are less
clogged and more disengaged.
Balsams and Resins distilled with the heat of boiling water yield
great quantities of a limpid, subtile, odoriferous, and, in one word,
essential Oil. In the still there remains a substance thicker and more
consistent than the Balsam or Resin was before distillation. The same
thing happens to essential Oils which by length of time have acquired
a consistence and are grown resinous. If they be re-distilled, they
recover their former tenuity, leaving behind them a remainder thicker
and more resinous than they themselves were. This second distillation
is called the _Rectification_ of an Oil.
It must be observed, that an essential Oil, combined with an acid
strong enough to dissolve it, immediately becomes as thick and
resinous, in consequence of this union, as if it had been long exposed
to the air: which proves the consistence an Oil acquires by long
keeping to be owing to this, that its lightest and less acid parts
being evaporated, the proportion of its acid to the remainder is so
increased, that it produces therein the same change, as an additional
acid mixed with the Oil would have wrought before the evaporation.
This also shews us, that Balsams and Resins are only essential Oils
combined with a great proportion of acid, and thereby thickened.
If vegetable substances, from which no more essential Oil can be drawn
by the heat of boiling water, be exposed to a stronger heat, they yield
an additional quantity of Oil; but it is thicker and heavier than the
essential Oil. These Oils are black, and have a very disagreeable burnt
smell, which hath made them be called _Fetid_ or _Empyreumatic_ Oils.
They are moreover very acrid.
It must be observed, that, if a vegetable substance be exposed to a
degree of heat greater than that of boiling water, before the fat or
the essential Oil is extracted from it, an empyreumatic Oil only will
then be obtained; because both the fat and essential Oils, when exposed
to the force of fire, are thereby burnt, rendered acrid, acquire a
smell of the fire, and, in a word, become truly empyreumatic. There
is ground to think, that an empyreumatic Oil is nothing else but an
essential or fat Oil burnt and spoiled by the fire, and that no other
Oil besides these two exists naturally in vegetables.
Empyreumatic Oils, distilled and rectified several times by a gentle
heat, acquire by every distillation a greater degree of tenuity,
lightness, and limpidity. By this means also they lose something of
their disagreeable odour; so that they gradually come nearer and
nearer to the nature of essential Oils: and if the rectifications be
often enough repeated, ten or twelve times for instance, they become
perfectly like those Oils; except that their smell will never be
so agreeable, nor like that of the substances from which they were
obtained.
Fat Oils may also be brought by the same means to resemble essential
Oils: but neither essential nor empyreumatic Oils are capable of
acquiring the properties of fat Oils.
SECTION III.
_Of_ ANIMAL OILS.
Distillation procures us considerable quantities of Oil from all
the parts of animal bodies, and especially from their fat. This Oil
at first is not very fluid, and is extremely fetid: but by many
rectifications it gradually acquires a great degree of clearness
and tenuity, and at the same time loses much of its disagreeable
odour. Animal Oils, thus rendered thin and fluid by a great number of
rectifications, have the reputation of being an excellent medicine, and
a specific in the epilepsy.
CHAP. XII.
_Of_ FERMENTATION _in general_.
By Fermentation is meant an intestine motion, which, arising
spontaneously among the insensible parts of a body, produces a new
disposition and a different combination of those parts.
To excite a Fermentation in a mixt body, it is necessary, first, that
there be in the composition of that mixt a certain proportion of
watery, saline, oily, and earthy parts: but this proportion is not
yet sufficiently ascertained. Secondly, it is requisite that the body
to be fermented be placed in a certain degree of temperate heat: for
much cold obstructs fermentation; and too much heat decomposes bodies.
Lastly, the concurrence of the air is also necessary to fermentation.
All vegetable and animal substances are susceptible of Fermentation,
because all of them contain in a due proportion the principles above
specified. However, many of them want the proper quantity of water, and
cannot ferment while they remain in such a state of dryness. But it is
easy to supply that defect, and so render them very apt to ferment.
With respect to minerals properly so called, (that is, excluding such
vegetable and animal substances as may have lain long buried in the
earth), they are not subject to any Fermentation; at least, that our
senses can perceive.
There are three sorts of Fermentation, distinguished from one another
by their several productions. The first produces wines and spirituous
liquors; for which reason it is called the _Vinous_ or _Spirituous
Fermentation_: the result of the second is an acid liquor; and
therefore it is called the _Acetous Fermentation_: and the third
generates an alkaline salt; which, however, differs from the alkaline
salts hitherto treated of, in this respect chiefly, that, instead of
being fixed, it is extremely volatile: this last sort takes the name
of the _Putrid_ or _Putrefactive Fermentation_. We shall now consider
these three sorts of Fermentation and their effects a little more
particularly.
These three sorts of Fermentation may take place successively in the
same subject; which proves them to be only three different degrees of
fermentation, all proceeding from one and the same cause, rather than
three distinct fermentations. These degrees of fermentation always
follow the order in which we have here placed them.
CHAP. XIII.
_Of the_ SPIRITUOUS FERMENTATION.
The juices of almost all fruits, all saccharine vegetable matters,
all farinaceous seeds and grains of every kind, being diluted with
a sufficient quantity of water, are proper subjects of Spirituous
Fermentation. If such liquors be exposed, in vessels slightly stopped,
to a moderate degree of heat, they begin in some time to grow turbid;
there arises insensibly a small commotion among their parts, attended
with a hissing noise; this by little and little increases, till the
grosser parts appear, like little seeds or grains, moving to and
fro, agitated among themselves, and thrown up to the surface. At the
same time some air bubbles rise, and the liquor acquires a pungent,
penetrating smell, occasioned by the very subtile vapours which exhale
from it.
These vapours have never yet been collected, in order to examine their
nature; and they are known only by their noxious effects. They are so
actively pernicious, that if a man comes rashly into a close place,
where large quantities of liquors are fermenting, he suddenly drops
down and expires, as if he were knocked on the head.
When these several phenomena, begin to go off, it is proper to stop
the fermentation, if a very spirituous liquor be required: for if it
be suffered to continue longer, the liquor will become acid, and from
thence proceed to its last stage, that is, to putrefaction. This is
done by stopping the containing vessels very close, and removing them
into a cooler place. Then the impurities precipitate, and settling at
the bottom leave the liquor clear and transparent: and now the palate
discovers that the sweet saccharine taste it had before fermentation is
changed to an agreeable pungency, which is not acid.
Liquors thus fermented are in general called _Wines_: for though in
common life that word properly signifies the fermented juice of grapes
only, and particular names are given to the fermented juices of other
vegetable substances; as that obtained from Apples is called _Cyder_;
that made from malt is called _Beer_: yet in Chymistry it is of use to
have one general term denoting every liquor that has undergone this
first degree of fermentation.
By distillation we draw from Wine an inflammable liquor, of a yellowish
white colour, light, and of a penetrating, pleasant smell. This
liquor is the truly spirituous part of the wine, and the product
of fermentation. That which comes off in the first distillation is
commonly loaded with much phlegm and some oily parts, from which it may
be afterwards freed. In this state it goes by the name of _Brandy_; but
when freed from these heterogeneous matters by repeated distillations,
it becomes still clearer, lighter, more fragrant, and much more
inflammable, and then is called _Spirit of Wine_, and _Rectified
Spirit of Wine_, or an _Ardent Spirit_, if considerably purified. The
properties which distinguish an Ardent Spirit from all other substances
are its being inflammable; its burning and consuming entirely, without
the least appearance of smoke or fuliginosity; its containing no
particles reducible to a coal; and its being perfectly miscible with
water. Ardent Spirits are lighter and more volatile than any of the
principles of the mixts from which they were produced, and consequently
more so than the phlegm, the acid, and the oil of which they themselves
consist. This arises from a particular disposition of these principles,
which are in a singular manner attenuated by fermentation, and thereby
rendered more susceptible of expansion and rarefaction.
Ardent spirits are supposed to be the natural solvents of oils and oily
matters. But it is very remarkable that they dissolve essential oils
only, without touching the fat of animals, or the fat oils obtained
from vegetables by expression; yet when these oils have once undergone
the action of fire, they become soluble in spirit of wine, and even
acquire a new degree of solubility every time they are distilled. It is
not so with essential oils, which can never be rendered more soluble in
ardent spirits than they are at first; and are so far from acquiring
a new degree of solubility every time they are distilled, that on the
contrary they even in some measure lose that property by repeated
rectifications.
I have taken some pains to find out the causes of these singular
effects, and the result of my inquiries is published among the Memoirs
of the Academy of Sciences for the year 1745. I therein consider ardent
spirits as consisting of an oil, or at least a phlogiston, mixed with a
portion of water, in which it is rendered soluble by means of an acid.
This being laid down, I shew that the inability of spirit of wine to
dissolve some oils must be imputed to its aqueous part, in which oils
are not naturally soluble without the intervention of a salt: and that
the power which this spirit exerts in dissolving other oils with ease,
such as essential oils, must in all probability be owing to this, that
in these oils it meets with the necessary saline medium, that is, with
an acid, which numberless experiments shew they actually contain.
On the other hand, I there prove, that the acid in essential oils is
super-abundant, and in some sort foreign to their nature, or that it
is but slightly connected with them, and in part deserts them every
time they are distilled; which renders them less soluble after every
new rectification: whereas, on the contrary, the fat expressed oils in
their natural state give not the least sign of acidity, but the action
of fire upon them discovers an acid which was not perceivable before.
Hence I conjecture, that these oils contain no more acid than is just
necessary to constitute them oils; that this acid is intimately blended
with their other component parts; that it is so sheathed and entangled
by these parts as to be incapable of exerting any of its properties;
and that on this account these oils in their natural state are not
soluble in spirit of wine: but that the disposition of their parts
being gradually changed by the fire, and their acid, being by that
means set more and more at liberty, at length recovers its properties,
and particularly that of rendering the oily parts soluble in an aqueous
menstruum: and hence it follows, that the fat oils become so much the
more soluble in spirit of wine the oftener they are exposed to the
action of fire.
Spirit of wine doth not dissolve fixed alkalis; or at least it takes
up but a very small quantity thereof; and hence ardent spirits may be
freed from much of their phlegm by means of these salts thoroughly
dried: for as they strongly imbibe moisture, and have even a greater
affinity than ardent spirits with water, if a fixed alkali, well
exsiccated, be mixed with spirit of wine that is not perfectly
dephlegmated, the alkali immediately attracts its superfluous moisture,
and is thereby resolved into a liquor, which, on account of its
gravity, descends to the bottom of the vessel. The spirit of wine,
which swims at top, is by this means as much dephlegmated, and as dry,
as if it had been rectified by several distillations. As it takes up
some alkaline particles in this operation, it is thereby qualified to
dissolve oily matters with the greater facility. When rectified in
this manner, it is called _Alcoholized Spirit of Wine_.
Yet spirit of wine, even when rectified to an alcohol, is not capable
of dissolving all oily matters. Those named Gums will by no means
enter into any sort of union therewith; but it readily dissolves most
of those which are known by the appellation of Resins. When it has
dissolved a certain proportion of resinous particles it acquires a
greater consistence, and forms what is called a _Spirit Varnish_, or a
_Drying Varnish_, because it soon dries. This Varnish is subject to be
damaged by water. Many sorts thereof are prepared, differing from each
other according to the different resins employed, or the proportions
in which they are used. Most of these Varnishes are transparent and
colourless.
Such bitumens or resins, as spirit of wine will not touch, are
dissolved in oils by means of fire, and then form another kind of
Varnish, which water does not hurt. These Varnishes are usually
coloured, and require much longer time to dry than the Spirit
Varnishes: they are called _Oil Varnishes_.
Spirit of wine hath a much greater affinity with water than with oily
matters: and therefore if a solution of any oil or resin in spirit of
wine be mixed with water, the liquor immediately grows turbid, and
acquires a whitish milky colour, owing entirely to the oily parts being
separated from the spirituous menstruum by the accession of water, and
too finely divided to appear in their natural form. But if the liquor
stand some time quiet, several of these particles unite together, and
gradually acquire a bulk sufficient to render them very perceptible to
the eye.
Acids have an affinity with spirit of wine, and may be combined with
it. By this union they lose most of their acidity, and on that account
are said to be _Dulcified_. But as these combinations of acids,
especially of the vitriolic acid, with spirit of wine furnish some new
productions of very singular properties, and as an examination thereof
may throw much light on the nature of ardent spirits, it will not be
amiss to take notice of them in this place, and consider each of them
particularly.
One part of highly concentrated oil of vitriol being mixed with four
parts of well dephlegmated spirit of wine, there arises immediately a
considerable ebullition and effervescence, attended with great heat,
and abundance of vapours, which smell pleasantly, but are hurtful to
the lungs. At the same time is heard a hissing like that produced by
a piece of red-hot iron plunged into water. Indeed it is proper to
mix the liquors very gradually; for otherwise the vessels in which the
operation is performed will be in great danger of breaking.
If the two liquors thus mixed be distilled with a very gentle heat,
there rises first a spirit of wine of a most penetrating and grateful
odour: when about half thereof is come over, what follows has a quicker
and more sulphureous smell, and is also more loaded with phlegm. When
the liquor begins to boil a little, there comes off a phlegm which
smells very strong of sulphur, and grows gradually more acid. On this
phlegm floats a small quantity of a very light and very limpid oil. In
the still there remains a thick blackish substance, somewhat like a
resin or bitumen. From this substance may be separated a good deal of a
vitriolic but sulphureous acid. When that is extracted, there remains
a black mass like a charred coal, which being put into a crucible, and
exposed to a violent heat, leaves a small portion of earth, very fixed,
and even vitrifiable.
By rectifying the ardent spirit, which came over in distilling the
above-mentioned mixture, a very singular liquor is obtained, which
differs essentially both from oils and from ardent spirits, though
in certain respects it resembles them both. This liquor is known in
Chymistry by the name of _Æther_, and its chief properties are as
follow.
Æther is lighter, more volatile, and more inflammable, than the most
highly rectified spirit of wine. It quickly flies off when exposed
to the air, and suddenly catches fire when any flame approaches it.
It burns like spirit of wine without the least smoke, and consumes
entirely without leaving the smallest appearance of a coal or of ashes.
It dissolves oils and oily matters with great ease and rapidity. These
properties it has in common with an ardent spirit. But it resembles
an oil in that it is not miscible with water; and this makes it
essentially different from spirit of wine, the nature of which is to be
miscible with all aqueous liquors.
Another very singular property of Æther is its great affinity with
gold, exceeding even that of _aqua regis_. It does not indeed dissolve
gold when in a mass, and in its metalline form; but if a small quantity
of Æther be added to a solution of gold in _aqua regis_, and the whole
shaken together, the gold separates from the _aqua regis_, joins the
Æther, and remains dissolved therein.
The reason of all the phenomena above-mentioned, resulting from the
mixture of spirit of wine with oil of vitriol, is founded on the great
affinity between this acid and water. For if the vitriolic acid be
weak, and as it were over-dosed with watery parts, neither oil nor
Æther can be obtained by means thereof: but when highly concentrated,
it attracts the aqueous parts very powerfully; and therefore, being
mixed with spirit of wine, lays hold of most of the water contained
in it, and even robs it of some portion of that which is essential to
its nature, and necessary to constitute it spirit of wine: whence it
comes to pass, that a certain quantity of the oily particles in its
composition being separated from the watery particles, and so brought
nearer to each other, they unite and assume their natural form; and
thus the oil that swims at top of the sulphureous phlegm is produced.
The vitriolic acid moreover thickens and even burns some of this oil;
and hence comes the bituminous residuum left at the bottom of the
still, which looks like the result of a vitriolic acid combined with
common oil. Lastly, the vitriolic acid becomes sulphureous, as it
always doth when united with oily matters, and also very aqueous, on
account of the quantity of phlegm which it attracts from the spirit of
wine.
Æther may be considered as a spirit of wine exceedingly dephlegmated,
even to such a degree that its nature is thereby changed; so that the
few aqueous particles left in it are not sufficient to dissolve the
oily particles and keep them asunder; which therefore being now much
nearer to one another than in common spirit of wine, the liquor hath
lost its property of being miscible with water.
Spirit of nitre well dephlegmated, and combined with spirit of wine,
presents likewise some very singular appearances.
First, in the very instant of its mixture with spirit of wine, it
produces a greater and more violent effervescence than the vitriolic
acid occasions.
Secondly, this mixture, without the help of distillation, and only by
stopping the bottle in which the liquors are contained, affords a sort
of Æther, produced probably by the vapours which ascend from, and swim
at top of the mixture. This is a very singular liquor. Dr. Navier was
the first that took notice of it, and gave a description thereof, which
may be seen in the Memoirs of the Academy of Sciences.
Thirdly, some authors pretend that, by distilling the mixture under
consideration, an oil is obtained greatly resembling that which, as we
observed above, rises from spirit of wine combined with the vitriolic
acid: others again deny this. For my part, I believe the thing depends
on the different concentration of the spirit of nitre, as well as on
the quality of the spirit of wine, which is sometimes more sometimes
less oily.
Fourthly, the two liquors we are speaking of, being intimately mixed by
distillation, form a liquor slightly acid, used in medicine, and known
by the name of _Sweet_ or _Dulcified Spirit of Nitre_: a very proper
name, seeing the nitrous acid, by uniting with the spirit of wine,
actually loses almost all its acidity and corrosive quality.
Fifthly and lastly, when the distillation is finished, there remains in
the bottom of the vessel a thick blackish substance, nearly resembling
that which is found after distilling oil of vitriol and spirit of wine.
Spirit of salt hath likewise been combined with spirit of wine; but it
does not unite therewith so easily or so intimately as the two acids
above-mentioned. To mix them thoroughly, the spirit of salt must be
highly concentrated, and smoking, and moreover the assistance of the
still must be called in. Some authors pretend that from this mixture
also a small quantity of oil may be obtained; which probably happens
when the liquors have the qualities above-specified. The marine acid
likewise, by uniting with spirit of wine, loses most of its acidity; on
which account it is in like manner called _Sweet_ or _Dulcified Spirit
of Salt_. A thick residuum is also found here after distillation.
CHAP. XIV.
_Of the_ ACETOUS FERMENTATION.
Besides an ardent spirit, wine affords a great deal of water, oil,
earth, and a sort of acid which shall be considered presently. When
the spirituous part is separated from these other matters, they
undergo no further change. But if all the constituent parts of wine
remain combined together, then, after some time, shorter or longer as
the degree of heat in which the wine stands is greater or less, the
fermentation begins afresh, or rather arrives at its second stage. The
liquor once more grows turbid, a new intestine motion arises, and,
after some days, it is found changed into an acid; which, however,
is very different from those hitherto treated of. The liquor then
takes the name of _Vinegar_. The acetous fermentation differs from
the spirituous, not only in its effect, but also in several of its
concomitant circumstances. Moderate motion is of service to this,
whereas it obstructs the spirituous; and it is attended with much more
warmth than the spirituous. The vapours it produces are not noxious,
like those of fermenting wine. Lastly, Vinegar deposites no tartar,
even when the wine employed in this operation is quite new, and hath
not had time to discharge its tartar: instead of tartar, Vinegar
deposites a viscid matter which is very apt to putrify.
It must be observed, that wine is not the only substance that is
susceptible of the acetous fermentation: for several vegetable and even
animal matters, which are not subject to the spirituous fermentation,
turn sour before they putrify. But as vinous liquors possess in a
very eminent degree the property of being susceptible of the acetous
fermentation, and likewise of producing the strongest acids that can
result from such fermentation, their acid shall be more particularly
considered in this place.
SECTION I.
_Of_ VINEGAR.
If wine, which has gone through this second stage of fermentation,
be distilled, instead of an ardent spirit, only an acid liquor is
obtained, which is called _Distilled Vinegar_.
This acid has the same properties as the mineral acids of which we have
already treated; that is, it unites with alkaline salts, absorbent
earths, and metallic substances, and therewith forms neutral saline
combinations.
Its affinity with these substances observes the same order as that
observed by the mineral acids with regard to the same substances;
but in general it is weaker; that is, any mineral acid is capable of
expelling the acid of Vinegar out of all matters with which it is
united.
Vinegar hath likewise a greater affinity than sulphur with alkalis:
whence it follows, that it is capable of decompounding that combination
of sulphur with an alkali called Liver of Sulphur, and of precipitating
the sulphur it contains.
The acid of Vinegar is always clogged with a certain proportion of
oily parts, which greatly weaken it, and deprive it of much of its
activity; and for this reason it is not near so strong as the mineral
acids, which are not entangled with any oil. By distillation, indeed,
it may be freed from this oil, and at the same time from the great
quantity of water which in a manner suffocates it, and by that means
may be brought much nearer to the nature of the mineral acids: but this
attempt hath not yet been prosecuted with the assiduity it deserves.
Besides distillation, there is another way of freeing Vinegar from a
good deal of its phlegm; and that is, by exposing it to a hard frost,
which readily congeals the watery part into ice, while the acid retains
its fluidity.
Vinegar, saturated with a fixed alkali, forms a neutral oily salt, of
a dark colour, which is semi-volatile, melts with a very gentle heat,
flames when thrown upon burning coals, and dissolves in spirit of wine,
of which, however, it requires six parts to complete the solution.
This solution being evaporated to dryness leaves a matter in the form
of leaves lying on each other; on which account it hath obtained the
name of _Terra Foliata_. The same foliated matter will be obtained,
though the salt be not previously dissolved in spirit of wine; but not
so readily. This salt is also called _Regenerated Tartar_. Under the
head of Tartar we shall see the reason of these different appellations.
Regenerated Tartar is also in some degree capable of crystallizing: for
this purpose a solution thereof in water must be slowly evaporated to
the consistence of a syrup, and then suffered to stand quiet in a cool
place; by which means it will shoot into clusters of crystals, lying
one upon another, not unlike the feathers on a quill.
With Vinegar and several absorbent earths, such as calcined pearls,
coral, shells of fish, _&c._ are also formed neutral saline compounds,
each of which takes the name of the particular earth employed in its
composition.
Vinegar perfectly dissolves Lead, and converts it to a neutral metallic
salt, which shoots into crystals, and has a sweet saccharine taste.
This compound is called _Sugar of Lead_, or _Sal Saturni_.
If Lead be exposed to the bare vapour of Vinegar, it will be thereby
corroded, calcined, and converted into a white matter much used in
painting, and known by the name of _Ceruse_; or, when it is finer than
ordinary, _White Lead_.
Vinegar corrodes Copper likewise, and converts it into a beautiful
green rust, which also is used in painting; and distinguished by the
name of _Verdegris_. However, Vinegar is not commonly employed to make
Verdegris: for this purpose they use wine, or the rape of wine, from
which fire extricates an acid analogous to that of Vinegar.
In treating of the several substances which constitute wine, we
mentioned an acid matter, but did not then enter into a particular
examination thereof; because as that matter greatly resembles the acid
of Vinegar, we thought it more proper to defer the consideration of its
properties till we had treated of the acetous fermentation, and its
effects.
SECTION II.
_Of_ TARTAR.
This substance is a saline compound, consisting of earthy, oily, and
especially acid parts. It is found in the form of crusts, adhering to
the inner sides of vessels in which wines have stood for some time,
particularly acid wines, such as those of Germany.
Tartar derives its origin from the super-abundant quantity of acid
contained in the juice of the grape. This superfluous acid, being more
than is requisite to constitute the ardent spirit, unites with some of
the oil and earth contained in the fermented liquor, and forms a kind
of salt; which for some time continues suspended in that liquor, but,
when the wine stands undisturbed in a cool place, is deposited, as hath
been said, on the sides of the cask.
Tartar in this state contains many earthy parts, which are superfluous,
and foreign to its nature. From these it may be freed by boiling
it repeatedly with a sort of earth found in the neighbourhood of
Montpelier, as may be seen in the Memoirs of the Academy of Sciences.
When it is purified, there appears on the surface of the liquor a sort
of white, crystalline pellicle, which is skimmed off as it forms. This
matter is called _Cream of Tartar_. The same liquor which produces this
Cream, and in which the purified Tartar is dissolved, being set to
cool, yields a great number of white semi-transparent crystals, which
are called _Crystals of Tartar_. The Cream and the Crystals of Tartar
are therefore no other than purified Tartar, and differ from each other
in their form only.
Though the Crystals of Tartar have every appearance of a neutral salt,
yet they are far from being such; for they have all the properties of
a true acid, which scarce differs from that of vinegar, except that it
contains less water, and more earth and oil; to which it owes its solid
form, as well as its property of not being soluble in water without
much difficulty: for a very great quantity of water is requisite to
keep the Crystals of Tartar in solution; and it must moreover be
boiling hot; otherwise as soon as it cools most of the Tartar dissolved
in it separates from the liquor, and falls to the bottom in the form of
a white powder.
Tartar is decomposed by calcination in the open fire. All its oily
parts are consumed or dissipated in smoke, together with most of its
acid. The other part of its acid, uniting intimately with its earth,
forms a very strong and very pure fixed alkali, called _Salt of Tartar_.
It will be shewn in its proper place, that almost every vegetable
matter, as well as Tartar, leaves a fixed alkali in its ashes: yet
Tartar has these peculiar properties; first, it assumes an alkaline
character even when burnt or calcined in close vessels, whereas other
substances acquire it only by being burnt in the open air; secondly,
the alkali of Tartar is stronger and more saline than almost any that
is obtained from other matters.
This alkali, when thoroughly calcined, powerfully attracts the moisture
of the air, and melts into an unctuous alkaline liquor, improperly
called _Oil of Tartar per deliquium_. This is the alkali generally used
in making the _Terra Foliata_, mentioned under the head of Vinegar;
for which reason this combination is called _Terra Foliata Tartari_; a
name suitable enough. But the same cannot be said of the other name,
_Regenerated Tartar_, which is also given it. It is true, that on this
occasion an oily acid is restored to the earth of the Tartar, analagous
to that of which the fire had deprived it: but the compound thence
resulting is a neutral salt which very readily dissolves in water;
whereas Tartar is manifestly acid, and not soluble, or at least hardly
soluble, in water.
Crystals of Tartar combined with alkali of Tartar produce a great
effervescence while they are mixing, as all acids usually do; and if
the combination be brought exactly up to the point of saturation, a
perfectly neutral salt is formed, which shoots into crystals, and
easily dissolves in water; and this hath procured it the name of
_Soluble Tartar_. It is also called the _Vegetable Salt_, as being
obtained from vegetables only; and again, _Tartarised Tartar_, because
it consists of the acid and the alkali of Tartar combined together.
Crystals of Tartar combined with alkalis procured from the ashes of
maritime plants, such as Soda, which alkalis resemble the basis of
sea-salt, form likewise a neutral salt, which crystallizes well, and
dissolves easily in water. This salt is another sort of soluble
Tartar. It is called _Saignette's Salt_, from the inventor's name.
Both the Vegetable Salt and Saignette's Salt are gently purgative
soaps, and much used in Medicine.
Tartar likewise dissolves the absorbent earths, as lime, chalk, _&c._
and with them forms neutral salts which are soluble in water[3]. It
even attacks metallic bodies, and when combined with them becomes
soluble. A soluble Tartar for medical use is prepared with Crystals of
Tartar and Iron: the metallic salt thereby produced hath the name of
_Chalybeated Soluble Tartar_. This salt attracts the moisture of the
air, and is one of those which do not crystallize.
[3] See Mr. Duhamel's Essays on this subject in the Memoirs of the
Academy of Sciences.
Crystallized Tartar acts also upon several other metallic substances:
for instance, it dissolves the Regulus, Liver, and Glass of Antimony,
and thence acquires an emetic quality: it is then called _Stibiated_ or
_Emetic Tartar_. It likewise dissolves Lead, and therewith forms a salt
which, in the figure of its crystals, resembles Tartarised Tartar.
It is very extraordinary that Tartar, which of itself is not soluble in
water, should be soluble therein when become a neutral salt by uniting
either with alkalis or with absorbent earths, or even with metals. With
respect to alkalis, indeed, it may be urged, that, having themselves
a great affinity with water, they communicate to Tartar some of that
facility with which they naturally unite therewith: but the same cannot
be alledged concerning absorbent earths, and metallic substances, which
water dissolves not at all, or at least with great difficulty, and in
small quantity. This effect, therefore, must be attributed wholly to
some change in the disposition of its parts which is to us unknown.
All the Soluble Tartars are easily decompounded by exposing them to a
certain degree of heat. In distillation they yield the same principles
which are obtained from Tartar; and what remains fixed in the fire,
after they are thoroughly burnt, is a compound of the alkali which
Tartar naturally produces, and of the alkaline or metallic substance
with which it was converted into a neutral salt.
As Crystal of Tartar is the weakest of all acids, on account of the
oily and earthy matters with which it is combined, Soluble Tartars are
decompounded by all the acids; by any of which crystal of Tartar may be
separated from the substance that serves it for a basis and renders it
a neutral salt.
The other acids which are procured from vegetables, and even those
which are obtainable from some animal substances, may all be referred
to and compared with either Vinegar or Tartar, according to the
quantities of oil or earth with which they are combined.
After all, these acids have not yet been thoroughly examined. There
is great reason to think that they are no other than the mineral
acids, which, in passing through the bodies of vegetables, and even of
animals, undergo a considerable change, especially by contracting an
union with oily matters. For, as we said before in treating of Vinegar,
by freeing them from their oil they are brought very near to the nature
of mineral acids; and so likewise the mineral acids acquire many of the
properties of vegetable acids by being combined with oils.
CHAP. XV.
_Of the_ PUTRID FERMENTATION, _or_ PUTREFACTION.
Every body which hath gone through the two stages of fermentation above
described, that is, the spirituous and the acetous fermentation, being
left to itself in a due degree of warmth, which varies according to
the subject, advances to the last stage of fermentation; that is, to
putrefaction.
It is proper to observe, before we go any further, that the converse
of this proposition is not true; that is, it is not necessary that a
body should successively pass through the spirituous and the acetous
fermentation, before it can arrive at the putrid; but that, as certain
substances fall into the acetous without having gone through the
spirituous fermentation, so others begin to putrify without having
undergone either the spirituous or the acetous fermentation; of which
last kind are, for instance, most animal substances. When therefore
we represented these three sorts of fermentation as three different
degrees or stages of one and the same fermentation, we supposed it to
be excited in a body susceptible of fermentation in its full extent.
However, there is still room to think that every substance which is
capable of fermenting always passes necessarily through these three
different stages; but that the substances most disposed thereto pass
with such rapidity through the first, and even the second, that they
arrive at the third before our senses can perceive the least signs of
either of the two former. This opinion is not destitute of probability:
yet it is not supported by proofs sufficiently strong and numerous to
compel our assent.
When a body is in a putrefying state it is easy to discover (as in the
two sorts of fermentation already treated of) by the vapours which rise
from it, by the opacity which invades it, if a pellucid liquor, and
frequently even by a greater degree of heat than is found in the two
other sorts of fermentation, that an intestine motion is begun among
its constituent parts, which lasts till the whole be entirely putrefied.
The effect of this intestine motion is in this, as in the two other
sorts of fermentation, to break the union, and change the disposition,
of the particles constituting the body in which it is excited, and to
produce a new combination. This is brought about by a mechanism to
which we are strangers, and concerning which nothing beyond conjectures
can be advanced: but these we neglect, resolving to keep wholly to
facts, as the only things in Natural Philosophy that are positively
certain.
If, then, we examine a substance that has undergone putrefaction, we
shall soon perceive that it contains a principle which did not exist in
it before. If this substance be distilled, there rises, first, by means
of a very gentle heat, a saline matter which is exceedingly volatile,
and affects the organ of smelling briskly and disagreeably. Nor is the
aid of distillation necessary to discover the presence of this product
of putrefaction: it readily manifests itself in most substances where
it exists, as any one may soon be convinced by observing the different
smell of fresh and of putrefied urine; for the latter not only affects
the nose, but even makes the eyes smart, and irritates them so as to
draw tears from them in abundance.
This saline principle which is the product of putrefaction, when
separated from the other principles of the body which affords it, and
collected by itself, appears either in the form of a liquor, or in that
of a concrete salt, according to the different methods used to obtain
it. In the former state it is called a _Volatile Urinous Spirit_; and
in the latter a _Volatile Urinous Salt_. The qualification of urinous
is given it, because, as was said, a great deal thereof is generated in
putrefied urine, to which it communicates its smell. It goes also by
the general name of a _Volatile Alkali_, whether in a concrete or in
a liquid form. The enumeration of its properties will shew why it is
called an alkali.
Volatile Alkalis, from whatever substance obtained, are all alike,
and have all the same properties; differing only according to their
degrees of purity. The Volatile Alkali, as well as the Fixed, consists
of a certain quantity of acid combined with and entangled by a portion
of the earth of the mixt body from which it was obtained; and on that
account it has many properties like those of a Fixed Alkali. But there
is moreover in its composition a considerable quantity of a fat or oily
matter, of which there is none in a Fixed Alkali; and on this account
again there is a great difference between them. Thus the Volatility of
the Alkali produced by putrefaction, which is the principal difference
between it and the other kind of Alkali whose nature it is to be Fixed,
must be attributed to the portion of oil which it contains: for there
is a certain method of volatilizing Fixed Alkalis by means of a fatty
substance.
Volatile Alkalis have a great affinity with acids, unite therewith
rapidly and with ebullition, and form with them neutral salts, which
shoot into crystals, but differ from one another according to the kind
of acid employed in the combination.
The neutral salts which have a Volatile Alkali for their basis are
in general called _Ammoniacal Salts_. That whose acid is the acid of
sea-salt is called _Sal Ammoniac_. As this was the first known, it gave
name to all the rest. Great quantities of this salt are made in Egypt,
and thence brought to us. They sublime it from the soot of cow's dung,
which is the fuel of that country, and contains sea-salt, together with
a Volatile Alkali, or at least the materials proper for forming it; and
consequently all the ingredients that enter into the composition of Sal
Ammoniac. See the Memoirs of the Academy of Sciences.
The neutral salts formed by combining the acids of nitre and of vitriol
with a Volatile Alkali are called, after their acids, _Nitrous Sal
Ammoniac_, and _Vitriolic Sal Ammoniac_: the latter, from the name of
its inventor, is also called Glauber's _Secret Sal Ammoniac_.
A Volatile Alkali, then, has the same property as a Fixed Alkali with
regard to acids: yet they differ in this, that the affinity of the
former with acids is weaker than that of the latter: and hence it
follows, that any Sal Ammoniac may be decompounded by a Fixed Alkali,
which will lay hold of the acid, and discharge the Volatile Alkali.
A Volatile Alkali will decompound any neutral salt which has not a
Fixed Alkali for its basis; that is, all such as consist of an acid
combined with an absorbent earth or a metallic substance. By joining
with the acids in which they are dissolved, it disengages the earths or
metallic substances, takes their place, and, in conjunction with their
acids, forms Ammoniac Salts.
Hence it might be concluded, that, of all substances, next to the
Phlogiston and the Fixed Alkalis, Volatile Alkalis have the greatest
affinity with acids in general. Yet there is some difficulty in this
matter: for absorbent earths, and several metallic substances, are also
capable of decompounding Ammoniacal Salts, discharging their volatile
Alkali, and forming new compounds by uniting with their acids. This
might induce us to think, that these substances have nearly the same
affinity with acids.
But it is proper to observe, that a Volatile Alkali decompounds such
neutral salts as have for their basis either an absorbent earth or a
metallic substance, without the aid of fire; whereas absorbent earths
or metallic substances will not decompound an Ammoniacal Salt, unless
they be assisted by a certain degree of heat.
Now, as all these matters are extremely fixed, at least in comparison
with a Volatile Alkali, they have the advantage of being able to resist
the force of fire, and so of acting in conjunction therewith; and fire
greatly promotes the natural action of substances upon one another:
whereas the Volatile Alkali in the Ammoniacal Salt, being unable to
abide the force of fire, is compelled to desert its acid; and that
so much the more quickly, as its affinity therewith is considerably
weakened by the presence of an earthy or metallic substance, both of
which have a great affinity with acids.
These considerations oblige us to conclude, that Volatile Alkalis
have a somewhat greater affinity, than absorbent earths and metallic
substances, with acids.
Ammoniacal Salts projected upon nitre in fusion make it detonate; and
the Nitrous Sal Ammoniac detonates by itself, without the addition of
any inflammable matter. This singular effect evidently demonstrates
the existence of an oily matter in Volatile Alkalis; for it is certain
that nitre will never deflagrate without the concurrence, and even the
immediate contact, of some combustible matter.
This oily substance is often found combined with Volatile Alkalis in
such a large proportion as to disguise it, in some measure, and render
it exceedingly foul. The salt may be freed from its superfluous oil by
repeated sublimations; and particularly by subliming it from absorbent
earths, which readily drink up oils. This is called the _Rectification_
of a Volatile Alkali. The salt, which before was of a yellowish or
dirty colour, by being thus rectified becomes very white, and acquires
an odour more pungent and less fetid than it had at first, that is,
when obtained by one single distillation from a putrid substance.
It is proper to observe, that the rectification of a Volatile Alkali
must not be carried too far, or repeated too often; for by that means
it may be entirely decomposed at length; and particularly if an
absorbent earth, and especially chalk, be employed for that purpose,
the salt may be converted into an oil, an earth, and water.
Volatile Alkalis act upon several metallic substances, and particularly
on copper; of which they make a most beautiful blue solution. On this
property depends a pretty singular effect, which happens sometimes when
we attempt, by means of a Volatile Alkali, to separate copper from
any acid with which it is combined. Instead of seeing the liquor grow
turbid, and the metal fall, both which generally happen when any Alkali
whatever is mixed with a metallic solution, we are surprised to observe
the solution of copper, upon adding a Volatile Alkali, retain its
limpidity, and let fall no precipitate; or at least, if the liquor does
grow turbid, it remains so but for a moment, and instantly recovers its
transparency.
This is occasioned by adding such a quantity of Volatile Alkali as
is more than sufficient fully to saturate the acid of the solution,
and considerable enough to dissolve all the copper as fast as it is
separated from the acid. On this occasion the liquor acquires a deeper
blue than it had before; which arises from the property which Volatile
Alkalis have of giving this metal, when combined with them, a fuller
blue than any other solvent can: hence we have a touchstone to discover
copper wherever it is; for let the quantity of this metal combined
with other metals be ever so small, a Volatile Alkali never fails to
discover it, by making it appear of a blue colour.
Though a Volatile Alkali be constantly the result of putrefaction, yet
it must not therefore be imagined that none can be produced by any
other means; on the contrary, most of those substances which contain
the ingredients necessary to form it, yield no inconsiderable quantity
thereof in distillation. Tartar, for example, which by being burnt in
an open fire is converted, as was shewn, into a Fixed Alkali, yields a
Volatile Alkali when it is decomposed in close vessels; that is, when
it is distilled; because, in this latter case, the oily part is not
dissipated or burnt, as it is by calcination in a naked fire, but has
time to unite with some of the earth and acid of the mixt, in such a
manner as to form a true Volatile Alkali.
To prove that on this occasion, as well as on all others, where
unputrefied bodies yield a Volatile Alkali, this salt is the product of
the fire, we need only observe, that in these distillations it never
rises till after some part of the phlegm, of the acid, and even of the
thick oil of the mixt, is come over; which never is the case when it is
formed beforehand in the body which is the subject of the operation, as
it is in those which have undergone putrefaction: for this salt, being
much lighter and more volatile than those other substances, rises of
course before them in distillation.
CHAP. XVI.
_A General View of_ CHYMICAL DECOMPOSITION.
Though we have considered all the substances which enter into the
composition of Vegetables, Animals, and Minerals, whether as primary or
as secondary principles, it will not be improper to shew in what order
we obtain these principles from the several mixts; and especially from
Vegetables and Animals, because they are much more complicated than
Minerals. This is called _Analysing_ a compound.
The method most commonly taken to decompose bodies is by applying to
them successive degrees of heat, from the gentlest to the most violent,
in appropriated vessels, so contrived as to collect what exhales from
them. By this means the principles are gradually separated from each
other; the most volatile rise first, and the rest follow in order, as
they come to be acted on by the proper degree of heat: and this is
called _Distillation_.